One of the byproducts of gas turbine engines used in power plants are exhaust gases, commonly known as flue gas, containing components which are harmful to the atmosphere such as oxides of nitrogen, (NOx). To prevent harm to the atmosphere and to the power plant itself, the levels of these harmful components must be controlled. Accordingly, various methods and processes have been developed for the reduction of these harmful components. A principal process for the removal of NOx from the flue gas is the injection of a reducing agent such as ammonia or any of a number of other known reducing agents. A common method is the selective catalytic reduction (SCR) process which involves the injection of ammonia (NH3) in the flue gas and then passing the flue gas over a catalyst. SCR processes are based on the reaction of NOx with ammonia in the presence of a catalyst to form nitrogen and water. These methods are effective within a narrow flue gas temperature window.
One traditional method of injecting into the flue gas stream uses an external ammonia vaporization system in which liquid ammonia, in an aqueous mixture, is first vaporized in a vaporization chamber and then routed to a distribution grid network for subsequent injection into the flue gas stream at a location upstream of an SCR reactor. The aqueous mixture is a mixture of combination of ammonia and water.
Areas of concern regarding the SCR process include ammonia breakthrough and a narrow operating temperature window. To address these concerns, it has been discovered that the aqueous mixture which has been heated to an operational temperature sufficient to cause vaporization, allows the SCR process to function.
The aqueous mixture is vaporized in a pre-heated vaporization chamber, prior to its introduction into the flue gas stream via the distribution grid network. If the aqueous mixture is introduced into the vaporization chamber prior to the time the vaporization chamber is pre-heated to the vaporization temperature, the aqueous mixture will not vaporize and will be introduced into the distribution grid network in a liquid state and will not be effective. It is, therefore, critical the vaporization chamber be pre-heated to a vaporization temperature prior to the introduction of the aqueous mixture.
The time needed to pre-heat a vaporization chamber is critical especially when its associated power plant will be called upon to provide electrical power within a short time frame. Thus, it is critical that the vaporization chamber be pre-heated to a vaporization temperature as quickly as possible.
The prior art typically heats the vaporization chamber through a convection process which uses a diffuser fan and an electric heater to blow hot air into the vaporization chamber. This process is very time consuming. Typically, the convection process takes longer to heat the vaporization chamber than the time to prepare the power plant's gas turbine engine. Thus, the power plant must wait for the vaporization chamber to pre-heat prior to becoming operational. Accordingly, there is a need for a system to provide for a more efficient and effective pre-heating of a vaporization chamber.